This application seeks support for a five-year study of auditory discrimination learning in children with autism and severe mental retardation and who characteristically respond unreliably to words spoken to them by parents, teachers, caretakers, and peers. The project has two main goals. The first goal is to define variables that influence acquisition of auditory stimulus control in this population. The second goal is to develop a comprehensive set of training procedures that will help to overcome certain fundamental problems in auditory discrimination. To accomplish these goals, we plan a two-stage series of studies. The first will be a program of laboratory research that uses methodologies that have in the past resulted in significant, well-documented gains in our knowledge of behavioral processes involved in discrimination learning. The second stage will be followup studies to determine whether auditory discrimination training will render children more likely to learn more complex performances that have auditory discrimination as a major prerequisite skill. Our Specific Aims are to develop procedures that: (a) establish the first instances of reliable auditory stimulus control in children who display exceptional difficulty in learning to respond to the presence vs. absence of a spoken word; (b) establish the first instances of differential auditory control in children who display control only by the presence vs. absence of a spoken word; (c) produce rapid acquisition of reliable differential auditory control, leading ultimately to the production of one-trial auditory discrimination learning; (d) teach children to report whether two successively presented auditory stimuli are the same or different, thereby establishing reliable control by auditory stimulus sequences; (e) determine the impact of auditory discrimination training on acquisition of auditory-visual conditional relations. Prior to the studies that focus on control by spoken words, many of the subjects will be tested to determine whether they demonstrate (f) responsiveness. to facilitated communication procedures or (g) atypical sensitivities to specific sound frequencies that might interact with pursuit of the specific aims above.